cagA, vacA, and iceA genotypes of Helicobacter pylori in Korean children

Antigenic Determinant of Helicobacter pylori FlaA for Developing Serological Diagnostic Methods in Children

The early diagnosis of Helicobacter pylori infection is important for gastric cancer prevention and treatment. Although endoscopic biopsy is widely used for H. pylori diagnosis, an accurate biopsy cannot be performed until a lesion becomes clear, especially in pediatric patients. Therefore, it is necessary to develop convenient and accurate methods for early diagnosis. FlaA, an essential factor for H. pylori survival, shows high antigenicity and can be used as a diagnostic marker. We attempted to identify effective antigens containing epitopes of high diagnostic value in FlaA. Full-sized FlaA was divided into several fragments and cloned, and its antigenicity was investigated using Western blotting. The FlaA fragment of 1345-1395 bp had strong immunogenicity. ELISA was performed with serum samples from children by using the 1345-1395 bp recombinant antigen fragment. IgG reactivity showed 90.0% sensitivity and 90.5% specificity, and IgM reactivity showed 100% sensitivity and specificity. The FlaA fragment of 1345-1395 bp discovered in the present study has antigenicity and is of high value as a candidate antigen for serological diagnosis. The FlaA 1345-1395 bp epitope can be used as a diagnostic marker for H. pylori infection, thereby controlling various gastric diseases such as gastric cancer and peptic ulcers caused by H. pylori.

Biomarker Characterization and Prediction of Virulence and Antibiotic Resistance from Helicobacter pylori Next Generation Sequencing Data

The Gram-negative bacterium Helicobacter pylori colonizes c.a. 50% of human stomachs worldwide and is the major risk factor for gastric adenocarcinoma. Its high genetic variability makes it difficult to identify biomarkers of early stages of infection that can reliably predict its outcome. Moreover, the increasing antibiotic resistance found in H. pylori defies therapy, constituting a major human health problem. Here, we review H. pylori virulence factors and genes involved in antibiotic resistance, as well as the technologies currently used for their detection. Furthermore, we show that next generation sequencing may lead to faster characterization of virulence factors and prediction of the antibiotic resistance profile, thus contributing to personalized treatment and management of H. pylori-associated infections. With this new approach, more and permanent data will be generated at a lower cost, opening the future to new applications for H. pylori biomarker identification and antibiotic resistance prediction.

Prevalence of Virulence Genes and Antigen Pattern in Helicobacter pylori-Infected Patients and The Level of Some Inflammatory Cytokines Compared with Non-infected Individuals

Background: The worldwide prevalence of Helicobacter pylori is about 50%. This bacterium needs a number of virulence factors for pathogenesis. Objectives: This study aimed to determine the prevalence of virulence genes (ureB, cytotoxin-associated gene A [cagA], and vacuolating cytotoxin [vacA]), as well as the antigenic profile in H. pylori strains. Methods: Eighty-five patients with abdominal pain, including 46 H. pylori-positive and 39 H. pylori-negative cases, were enrolled in this study. The serum levels of interleukin (IL)-17F, tumor necrosis factor α (TNF-α), and interferon γ (IFN-γ) cytokines were measured by multiplex kits and flow cytometry. After molecular identification by the ureC gene, vacA, cagA, and ureB genes were detected by polymerase chain reaction (PCR). Finally, after antigenic extraction, the whole-cell protein was exhibited by sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS-PAGE). Results: The prevalence of vacA, ureB, and cagA genes were 91.3%, 67.39%, and 50%, respectively. The frequency of genes and cell surface antigens were not significantly different based on the gastritis severity (P > 0.05). IL-17F significantly (P = 0.046) increased in the presence of 19.5 kDa (outer membrane protein [OMP]). Moreover, the OMP antigen significantly enhanced immunoglobulin A (IgA; P = 0.013). In the presence of the 66-kDa (ureB) antigen, the serum level of IFN-γ increased (p = 0.041). Finally, the CagA protein led to increased IgG antibody levels (p = 0.027). Conclusions: Early detection of H. pylori infection can play a crucial role in managing it. Our results suggest that IL-17F, TNF-α, and IFN-γ cytokines could be diagnostic markers. However, further studies are required to fully investigate this suggestion.

How did the ancient bacterium, Helicobacter pylori, cause an epidemic of chronic duodenal ulceration?

The association of Helicobacter pylori with chronic duodenal ulceration was a seminal observation in the short history of gastroenterology. However, H. pylori is now known to be an ancient bacterium, whereas there is persuasive evidence that the epidemic of duodenal ulceration began in the second half of the 19th century and continued into the second half of the 20th century. Possible explanations for the epidemic include genomic changes in the organism and environmental or other influences on the human host. While genomic changes resulted in the appearance of virulence factors, these seem likely to have appeared thousands of years ago with minimal effects on gastritis because of coexisting suppression of gastric immunity. In contrast, the emergence of duodenal ulceration is best explained by a change in the pattern of gastritis from inflammation involving the antrum and body in most individuals to a significant minority (10-20%) with antral gastritis but with relative sparing of the body of the stomach. In the latter group, the increase in serum gastrin (particularly G17) associated with antral gastritis had trophic effects on gastric parietal cells with an increase in the parietal cell mass and hypersecretion of gastric acid. Hypersecretion of acid is seen as the major risk factor for duodenal ulceration with significant contributions from environmental factors including smoking and use of nonsteroidal, anti-inflammatory drugs. Host factors favoring changes in the pattern of gastritis include delayed acquisition of infection and improved nutrition; both with enhancing effects on mucosal immunity.

Increased Risk of Severe Gastric Symptoms by Virulence Factors vacAs1c, alpA, babA2, and hopZ in Helicobacter pylori Infection

Two virulence factors of Helicobacter pylori, cagA and vacA, have been known to play a role in the development of severe gastric symptoms. However, they are not always associated with peptic ulcer or gastric cancer. To predict the disease outcome more accurately, it is necessary to understand the risk of severe symptoms linked to other virulence factors. Several other virulence factors of H. pylori have also been reported to be associated with disease outcomes, although there are many controversial descriptions. H. pylori isolates from Koreans may be useful in evaluating the relevance of other virulence factors to clinical symptoms of gastric diseases because the majority of Koreans are infected by toxigenic strains of H. pylori bearing cagA and vacA. In this study, a total of 116 H. pylori strains from Korean patients with chronic gastritis, peptic ulcers, and gastric cancers were genotyped. The presence of virulence factors vacAs1c, alpA, babA2, hopZ, and the extremely strong vacuolating toxin was found to contribute significantly to the development of severe gastric symptoms. The genotype combination vacAs1c/alpA/babA2 was the most predictable determinant for the development of severe symptoms, and the presence of babA2 was found to be the most critical factor. This study provides important information on the virulence factors that contribute to the development of severe gastric symptoms and will assist in predicting clinical disease outcomes due to H. pylori infection.

Helicobacter pylori virulence genes

Helicobacter pylori (H. pylori) is one of the most important human pathogens, infecting approximately half of the global population. Despite its high prevalence, only a subset of H. pylori infected individuals develop serious gastroduodenal pathology. The pathogenesis of H. pylori infection and disease outcome is thus thought to be mediated by an intricate interplay between host, environmental and bacterial virulence factors. H. pylori has adapted to the harsh milieu of the human stomach through possession of various virulence genes that enable survival of the bacteria in the acidic environment, movement towards the gastric epithelium, and attachment to gastric epithelial cells. These virulence factors enable successful colonization of the gastric mucosa and sustain persistent H. pylori infection, causing chronic inflammation and tissue damage, which may eventually lead to the development of peptic ulcers and gastric cancer. Numerous studies have focused on the prevalence and role of putative H. pylori virulence genes in disease pathogenesis. While several virulence factors with various functions have been identified, disease associations appear to be less evident, especially among different study populations. This review presents key findings on the most important H. pylori virulence genes, including several bacterial adhesins and toxins, in children and adults, and focuses on their prevalence, clinical significance and potential relationships.

Helicobacter pylori Pathogenicity Factors Related to Gastric Cancer

BACKGROUND

Although the causal relationship between Helicobacter pylori infection and the development of gastric cancer is firmly established, the exact nature of the pathogenicity factors of H. pylori that predispose to gastric oncogenesis remains incompletely characterized. We investigated the association between H. pylori virulence genotypes and disease in a well-characterized cohort consisting of 109 H. pylori isolates from gastric biopsies originating from patients.

METHODS

The prevalence of genotype was assessed by PCR and related to clinical histopathological parameters.

RESULTS

The relation of babA2 and babB negative and iceA1 positive genotype as a single genotype and the development of cases to GC was statistically significant (P < 0.001). The cagE, cagA, and iceA1 were found more commonly in patients with GC as compared with the other groups. The relation of the presence of iceA1 and the development of cases to GC was statistically significant (P = 0.008), but babA2 and babB alleles were not detected in these patients. These apparent negative associations were still statically significant (P = 0  and 0.005).

CONCLUSION

Our results show an elevated prevalence of infection with H. pylori strains carrying known virulence genotypes with high genetic diversity. This highlights the importance of identifying gene variants for an early detection of virulent genotypes.

Correlations between the CagA Antigen and Serum Levels of Anti-Helicobacter pylori IgG and IgA in Children

We tested correlations between anti-Helicobacter pylori IgG and IgA levels and the urease test, anti-CagA protein antibody, degree of gastritis, and age. In total, 509 children (0-15 years) were enrolled. Subjects were stratified as 0-4 years (n = 132), 5-9 years (n = 274), and 10-15 years (n = 103) and subjected to the urease test, histopathology, ELISA, and western blot using whole-cell lysates of H. pylori strain 51. The positivity rate in the urease test (P = 0.003), the degree of chronic gastritis (P = 0.021), and H. pylori infiltration (P < 0.001) increased with age. The median titer for anti-H. pylori IgG was 732.5 IU/mL at 0-4 years, 689.0 IU/mL at 5-9 years, and 966.0 IU/mL at 10-15 years (P < 0.001); the median titer for anti-H. pylori IgA was 61.0 IU/mL at 0-4 years, 63.5 IU/mL at 5-9 years, and 75.0 IU/mL at 10-15 years (P < 0.001). The CagA-positivity rate was 26.5% at 0-4 years, 36.5% at 5-9 years, and 46.6% at 10-15 years for IgG (P = 0.036), and 11.3% at 0-4 years, 18.6% at 5-9 years, and 23.3% at 10-15 years for IgA (P < 0.001). Anti-H. pylori IgG and IgA titers increased with the urease test grade, chronic gastritis degree, active gastritis, and H. pylori infiltration. Presence of CagA-positivity is well correlated with a high urease test grade and high anti-H. pylori IgG/IgA levels.

Prevalence of Helicobacter pylori virulence genotypes among children in Eastern Turkey

AIM: To identify the virulence genotypes of Helicobacter pylori (H. pylori) if present in children in Eastern Turkey and if those genotypes are mostly associated with severe clinical presentations.

METHODS: A total of 49 H. pylori positive Turkish children (42 with antral nodularity and 7 with peptic ulcer) who underwent upper gastrointestinal endoscopy with abdominal symptoms during the period from March 2011 to September 2012 were enrolled in this study. Antral nodularity was diagnosed endoscopically by two of the authors. We determined for the presence of cagA, vacA, cagE, iceA and babA2 genotypes of H. pylori isolates in DNA obtained directly from frozen gastric biopsy samples by polymerase chain reaction test using specific primers.

RESULTS: Of the 49 H. pylori isolates studied, 61.2%, 91.8%, 22.4%, 28.6%, 57.1% and 40.8% were positive for the cagA, vacA s1, cagE, iceA1, iceA2 and babA2 genes, respectively. We showed that the most common vacA subtype was s1a (79.6%). However, the s2 gene was found less frequently with an isolation rate of 8.2% of the H. pylori isolates. The genotypes iceA2 and vacA s1m2 were the most frequently found types in children with antral nodularity. In addition, the genotypes iceA1, babA2 and vacA s1m1 were found in similar ratios in all the H. pylori isolates obtained from children with peptic ulcer. The genotypes vacA s2m1 and s1c were not observed in any of isolates studied.

CONCLUSION: This study showed that vacA s1m2, cagA and iceA2 were the most common genotypes, and no association between antral nodularity and genotypes was observed.

Helicobacter pylori: detection of iceA1 and iceA2 genes in the same strain in Mexican isolates

BACKGROUND AND AIMS

Helicobacter pylori iceA1 and iceA2 gene amplification is usually performed to identify mixed populations as both genes are apparently reportedly exclusive. However, some strains isolated from Mexico show both iceA genes. The aim of this study was to establish the frequency of these genes in Mexican isolates and genomic diversity of the H. pylori strains.

METHODS

One hundred thirty six biopsies were obtained from 68 patients (39 children and 29 adults). The presence of H. pylori was confirmed in 3/18 children and 6/19 adults by culture. There were 93 clinical strains isolated from nine patients. Additionally, we studied 37 strains from a strain collection isolated from 10 patients. The strains were genotyped and dual iceA genes were identified by polymerase chain reaction (PCR) and amplicons were sequenced. In addition, an enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) assay was performed as fingerprinting method.

RESULTS

The genotypification of the H. pylori isolates indicated that all strains were vacA+; 86% babA2+, 86% cagA+, 82% vacA s1m1+, 19% iceA1+, 9% iceA2+, and 72% of them carried both iceA1 and iceA2 genes. The ERIC-PCR profiling revealed that the strains clustered in eight genetic groups depending on the presence of iceA1, iceA2 or both. A basic local multiple alignment analysis of the nucleotide sequences revealed that the iceA1 and iceA2 genes exhibited no relevant similarity.

CONCLUSION

The results here showed the presence of triple-positive strains (babA, cagA, vacA) of H. pylori and strains carrying simultaneously both iceA1 and iceA2 genes.

Gastric phenotype in children with Helicobacter pylori infection undergoing upper endoscopy

INTRODUCTION

Helicobacter pylori is a definite risk factor for the development of gastric cancer, especially in the context of corpus-predominant gastritis. The infection is usually acquired in early childhood, implying lifelong exposure to this carcinogen if untreated. Our objective was to analyze the prevalence of H. pylori induced corpus-predominant gastritis in children.

MATERIAL AND METHODS

We analyzed the results of 265 esophagogastroduodenoscopies (EGD) in children performed between February 2006 and August 2008; 34 endoscopies were excluded (24 with follow-up investigations, 5 with incomplete data, 5 adults). H. pylori gastritis was defined by the presence of H. pylori in histology or by a positive rapid urease test. Grade of inflammation was rated according to the updated Sydney Scoring System. Gastritis was classified as corpus-predominant when the degree of chronic inflammation was higher in the corpus than in the antrum and vice versa for antrum-predominant gastritis.

RESULTS

Two hundred thirty-one patients (128 female; mean age ± SEM: 10.5 ± 3.5 years) were analyzed. Eighty-four (36%) were H. pylori positive, 147 (64%) patients were negative for H. pylori. In H. pylori positive patients, 39 (46%) patients had pangastritis (one patient with mucosal atrophy, which is regarded as precancerous lesion), 42 (50%) had antrum-predominant gastritis and 3 (4%) had corpus-predominant gastritis. One female patient (15.6 years old) with severe (grade 3) pangastritis had focal mucosal atrophy in both antrum and corpus, but no patient had intestinal metaplasia.

CONCLUSIONS

Corpus-predominant gastritis develops in H. pylori infected children, while mucosal atrophy and intestinal metaplasia develop later in the course of the infection.

Prevalence of Helicobacter pylori vacA, cagA and iceA genotypes in South African patients with upper gastrointestinal diseases

Clinical response to Helicobacter pylori infection may be determined by specific virulence-associated genotypes which varies geographically. The aim of this study was to investigate the diversity of putative virulence markers of H. pylori; cagA, vacA and iceA in the Eastern Cape Province of South Africa. One hundred H. pylori strains obtained from dyspeptic patients were used. Gastric biopsies were obtained from 254 dyspeptic patients. H. pylori was cultured and strains were studied. Bacterial genotypes cagA, vacA (s and m subtypes) and iceA were analysed by PCR using specific primers. CagA was identified in 90% of the strains investigated. Fifty-eight of the 100 strains had the vacA signal sequence genotype s1 and 26 had subtype s2. Combined vacA s1/s2 was detected in 16 of the strains. VacA middle region analysis showed that 8 (8%) strains were m1 while 50 were m2. Combined vacA m1/m2 was detected in 36 of the strains. s1m2 (20%) and s2m2 (20%) genotypes were the most common allelic combinations of the vacA gene among the strains. Multiple vacA genotypes were detected in this study. Twenty-six percent of the strains identified had both iceA1 and iceA2. All our strains tested positive for the ureC (glmM) gene. This study reveals a high prevalence of vacA, cagA and iceA2.

High prevalence of clarithromycin resistance and cagA, vacA, iceA2, and babA2 genotypes of Helicobacter pylori in Brazilian children

We isolated 45 Helicobacter pylori strains from 217 child patients. Resistance to clarithromycin, metronidazole, amoxicillin, and tetracycline was detected in 27%, 13%, 4%, and 0% of strains, respectively. The A2143G mutation was the most prevalent (67%) among clarithromycin-resistant strains. In addition, strain genotyping revealed a significant association between gastritis severity and the simultaneous presence of cagA, vacA s1m1, iceA2, and babA2 genes.

Helicobacter pylori in a Korean isolate expressed proteins differentially in human gastric epithelial cells

PURPOSE

The proteins expressed in gastric epithelial cells infected with Helicobacter pylori (H. pylori) may determine the clinical outcome such as chronic gastritis, peptic ulcer, and gastric carcinoma. The present study aims to determine the differentially expressed proteins in human gastric epithelial AGS cells that were infected with H. pylori in a Korean isolate, a cagA+, vacA s1b m2 iceA1 H. pylori by proteomic analysis. The differentially expressed proteins, whose expression levels were more or less than twofold in H. pylori-infected cells, were analyzed.

RESULTS

Ten proteins (chromatin assembly factor-1, proliferating cell nuclear antigen, 14-3-3 protein tau, eukaryotic translation initiation factor 6, heat-shock protein 90beta, dimethylarginine dimethylaminohydrolase-1, L-lactate dehydrogenase B chain, prohibitin, triosephosphate isomerase, protein disulfide isomerase) were up-regulated while eight proteins (heat-shock gp96 precursor, nucleophosmin, ornithine aminotransferase, Ku70, L-arginine-glycine amidinotransferase, Smad anchor for receptor activation, ADP-ribosylation factor, WD repeat-containing protein isoform 1) were down-regulated by H. pylori infection in AGS cells. These proteins are related to cell proliferation, cell adhesion, carcinogenesis, cell-defense mechanisms against oxidative stress, membrane trafficking, and energy metabolism.

CONCLUSIONS

Oxidative stress, cell proliferation, cell adhesion, and membrane trafficking may be involved in the pathogenesis of gastric diseases including cancer associated with H. pylori in a Korean isolate.

Helicobacter pylori infection in pediatrics

his review summarizes the articles published on Helicobacter pylori infection in children between April 2008 and March 2009. Recent evidence highlights the decreasing prevalence trend of H. pylori infection and supports both intrafamilial and extrafamilial transmission. The association with various symptoms is still being debated. Interestingly, H. pylori infection seems inversely associated with allergic diseases. Monoclonal stool antigen tests are widely used and accurate for the diagnosis of H. pylori infection, but less accurate in young children. The new biprobe real-time PCR assay applied to stools showed a poor sensitivity in children. Using the urea hydrolysis rate next to the delta over baseline values, the (13)C-urea breath test provides excellent results for all age children, even for young children. Treatment of H. pylori infection remains a challenge, considering suboptimal efficacy of current therapy. Among emerging alternatives, sequential treatment appears promising. The adjunction of probiotics to conventional regimens, although eliciting great interest, has shown limited therapeutic benefit.

Association of cagA and iceA genotypes with Helicobacter pylori related diseases in Xi'an area

AIM: To study the impact of cagA, iceA genes and their synergy on the outcome of H pylori infection so as to explore the dominant genotypes of H pylori that induce certain diseases in Xi'an area.

METHODS: One hundred and one H pylori-positive specimens from the patients after gastroscopy were preliminarily selected using the rapid urease test (RUT) and 91 eligible cases were chosen from them using the method of polymerase chain reaction (PCR) to amplify ureC. The subtypes of cagA, iceA genes were detected by PCR and agarose gel electrophoresis. Relationship between different combinations of genotypes and disease was analyzed using χ² test and Fisher exact test.

RESULTS: The cagA-positive rate was 79.1%, and the overall detection rate of iceA was 75.82%, in which the detection rate oficeA1 was 50.5% and that of iceA2 was 38.5%. The positive rate of cagA⁺/iceA1⁺ was higher than that of other groups. Each gene alone or genes in different combinations didn't show any statistical significance in clinical outcomes. The relevance existed in iceA and cagA. 229 bp, 334 bp, 439 bp, 549 bp and 229 bp+334 bp fragments of the genes were found in iceA2.

CONCLUSION: cagA⁺/iceA1⁺ is the dominant genotype of H pylori in Xi'an area. Neither a single gene nor the combination of cagA, iceA1, iceA2 are helpful in predicting the clinical outcome of H pylori infection. We may find synergy with the iceA and cagA. iceA2 shows greater variability in Xi'an area.